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404a pressures in low

I have a r-404a roof-top condensing serving a walk in freezer. pressures are 235 psi head pressure and a 28psi suction pressure. Outdoor ambient is 30degress and indoor box temperature is about 20degrees. System has a head pressure control on roof for hot gas. Wondering if pressures sound right. Seems like head pressure should be lower but not sure. Was at job last week and found a 260 head pressure. Reclaimed a little bit to bring down head pressure but sight glass was still full

The head is too high but not high enough to keep the suction pressure up. You need to determine why you have high head, but I don't think thats the cause of the problem. Did you get a SH reading @ the coil?

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Checked pressures again after box dropped from 35 degrees to 10 degrees after running for a few... 23 psi suction, 225psi head pressure. 20 degree super heat at evap coil. Total system super-heat is 40 degrees. I also have a 10 degree superheat where the liquid from the accumulator passes across the suction line, not sure what it's called but thought I would mention it. Last, the sporlan head pressure control which I believe might have something to do with it. The readings for the valve are. Hot gas inlet - 145 degrees, condenser coil liquid inlet- 42 degrees, valve outlet going to receiver than system-73 degrees. Thanks in advance.

SH too high at evaporator. You are starving the evaporator. Most guys set TXV for 5 or 6 degrees at evap for a freezer. The bulb is securely wrapped and making good contact? Check this first if you haven't already.

Checked pressures again after box dropped from 35 degrees to 10 degrees after running for a few... 23 psi suction, 225psi head pressure. 20 degree super heat at evap coil. Total system super-heat is 40 degrees. I also have a 10 degree superheat where the liquid from the accumulator passes across the suction line, not sure what it's called but thought I would mention it. Last, the sporlan head pressure control which I believe might have something to do with it. The readings for the valve are. Hot gas inlet - 145 degrees, condenser coil liquid inlet- 42 degrees, valve outlet going to receiver than system-73 degrees. Thanks in advance.

Sounds like the headmaster is working properly. The headmasters are stamped with a pressure, but that doesn't mean the system head pressure will always be exactly what that valve is rated at. I have seen 180# headmasters that bypass and maintain a 170# head and they work just fine. In your case, a 215# valve bypassing at 225# sounds just fine to me.

Yes evaporator superheat sounds high. Confirm the sightglass is clear and solid column of liquid before adjusting the TXV. Good luck!